It has been known heretofore in the prior art to utilize any one of three different types of power tool systems, i.e., hydraulic, pneumatic, and electric. In comparing the relative advantages of the three types of systems, it has been found however, that a hydraulically operated system possesses several advantages relative to the other two. For example, because hydraulically operated tools are powered by oil, they are self-lubricating. Therefore, they do not require the expensive air dryers which are commonly required for example, in air systems to prevent corrosion. Also, hydraulically operated systems won't freeze up in cold weather, thereby saving time which otherwise would be required to unfreeze the system as well as assisting to keep maintenance costs at a minimum.
Another desirable characteristic of hydraulic power tool systems is that they are relatively lightweight. This means therefore, that they are much easier to handle on the job and for much longer periods of time. In addition, they are much more easily moved from one job to the next. With regard further to the matter of mobility, hydraulic power tools do not require bulky expensive compressors. In fact, such tools may be used virtually anywhere. They can operate off a truck, tractor, backhoe or any other available hydraulic source. On the other hand, if extra power is required for multi-tool operations, they are also capable of being used with one of the portable hydraulic units which are presently commercially available.
A further desirable characteristic of hydraulic power tools is that they are inherently relatively quiet. As a result, no costly noise reduction alterations, which commonly are required in other systems, are needed. Noise level ordinances now being passed in cities across the country make built-in quietness an even more attractive feature for a power tool system to possess.
To thus summarize, a hydraulic power tool system enjoys the following advantageous characteristics. It is characterized by having high power-to-weight performance. It provides low cost operation and maintenance. In addition, it is quiet in operation and is capable of being easily handled by virtue of its light weight.
Notwithstanding the fact that the hydraulic power tool systems which have typically been available in the prior art heretofore have embodied the characteristics which have been discussed herein above, there has nevertheless existed the need to provide such a power tool system which would be simpler in construction. There are numerous reasons why it is desirable to be able to provide a hydraulic power tool system which has a construction that is simpler than those previously known. For example, simplifying the construction provides economy of manufacture by virtue of the fact that fewer parts need to be produced and also economy of assembly since less time and effort is required to assemble the components which comprise the system. In addition, by simplifying the construction a further reduction is capable of being effected in the weight of the hydraulic power tool system thereby further improving the power-to-weight performance of the system. Finally, the maintenance requirements with a simpler construction are obviously less than those which are to be expected with a more complex structure just by virtue of the increased number of parts in the latter structure which need attention from a maintenance standpoint apart from any other consideration which may be applicable in this regard.
Accordingly, it is an object of the present invention to provide a novel and improved hydraulic power tool and more particularly, a fluid operated breaker which possesses a high power-to-weight ratio thereby providing increased efficiency and also lessening operator fatigue.
It is also an object of the present invention to provide such a hydraulic power tool which embodies a stepped, pilot operated valve which allows small pilot areas to control large flows in a simple and compact manner.
A further object of the present invention is to provide such a hydraulic power tool which embodies an accumulator system which is operable to store energy for subsequent release under preselected conditions, at a predetermined time interval, etc. and which includes vent means operable for venting any leakage of fluid or gas to prevent contamination of one with the other.
A still further object of the present invention is to provide such a fluid operated breaker which is capable of being employed to drive tools of the type presently known in the prior art.
Yet another object of the present invention is to provide such a fluid operated breaker which has a simplified construction that enables economies of manufacture and assembly to be effected.